Inorganic Graphenylene: A Porous Two-Dimensional Material With Tunable Band Gap

By means of ab initio calculations we investigate the possibility of existence of a boron nitride (BN) porous two-dimensional nanosheet which is geometrically similar to the carbon allotrope known as biphenylene carbon. The proposed structure, which we called Inorganic Graphenylene (IGP), is formed spontaneously after selective dehydrogenation of the porous Boron Nitride (BN) structure proposed by Ding et al. We study the structural and electronic properties of both porous BN and IGP and it is shown that, by selective substitution of B and N atoms with carbon atoms in these structures, the band gap can be significantly reduced, changing their behavior from insulators to semiconductors, thus opening the possibility of band gap engineering for this class of two-dimensional materials

Investigation of three-dimensional effects on a cavitating Venturi flow

International audienceA numerical investigation of the behaviour of a cavitation pocket developing along a Venturi geometry has been performed using a compressible one-fluid hybrid RANS/LES solver. The interplay between turbulence and cavitation regarding the unsteadiness and structure of the flow is complex and not well understood. This constitutes a determinant point to accurately simulate the dynamic of sheet cavities. Various turbulent approaches are tested: a new Scale-Adaptive model and the Detached Eddy Simulation. 2D and 3D simulations are compared with the experimental data. An oblique mode of the sheet is put in evidence

Modelling for isothermal cavitation with a four-equation model

International audienceIn a recent study, an original formulation for the mass transfer between phases has been proposed to study one-dimensional inviscid cavitating tube problems. This mass transfer term appears explicitly as a source term of a void ratio transport-equation model in the framework of the homogenous mixture approach. Based on this generic form, a two-dimensional preconditioned Navier-Stokes one-fluid solver is developed to perform realistic cavitating flows. Numerical results are given for various inviscid cases (underwater explosion, bubble collapse) and unsteady sheet cavitation developing along Venturi geometries at high Reynolds number. Comparisons with experimental data (concerning void ratio and velocity profiles, pressure fluctuations) and with a 3-equation model are presented

Turbulence model and numerical scheme assessment for buffet computations

International audienceThe prediction of shock-induced oscillations over transonic rigid airfoils is important for a better understanding of the buffeting phenomenon. The unsteady resolution of the Navier-Stokes equations is performed with various transport-equation turbulence models in which corrections are added for nonequilibrium flows. The lack of numerical efficiency due to the CFL stability condition is circumvented by the use of a wall law approach and a dual time stepping method. Moreover, various numerical schemes are used to try and be independent of the numerical discretization. Comparisons are made with the experimental results obtained for the supercritical RA16SC1 airfoil. They show the interest in using the SST correction or realizability conditions to get correct predictions of the frequency, amplitude and pressure fluctuations over the airfoil

Numerical simulations of a transport-aircraft configuration

International audienceAn implicit low-cost Navier-Stokes solver combined with a multigrid algorithm and wall functions has been developed for efficient numerical simulations on a realistic wing-body aircraft configuration. A study of the behavior of different transport-equation turbulence models is given. Comparisons are made with experimental data. The structure of the three-dimensional flow separation predicted by computations is described and its topological coherence is checked

Evidence for exercise training in autonomic function modulation in patients with chronic obstructive pulmonary disease (COPD) : a systematic review

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